1. Field of the Invention
The present invention generally relates to a circuit structure and a manufacturing method thereof, and more particularly, to a circuit structure disposed on a circuit substrate and a manufacturing method of the circuit structure.
2. Description of Related Art
In this information society, people are pursuing products with high speed, high quality and multifunction. As to the product appearance, it is trending toward light, thin and small. Typical electronic products include a chip and a substrate (e.g., chip carrier) connected to the chip. The chip includes an active surface with a plurality of bumps (e.g., gold bumps) disposed thereon, and is electrically connected to a circuit structure of the substrate by flip-chip bonding. The chip can receive a signal from or transmit a signal to the circuit structure of the substrate via the bumps. Therefore, the high reliability of the connecting between the bumps and the circuit structure of the substrate is critically important to the quality of signal transmission.
In addition, a thermal stress may be generated between the chip and the substrate due to unmatched coefficient of thermal expansion. Therefore, an underfill is typically filled in between the chip and the substrate to enclose the bumps to avoid transverse crack of the bumps that could result from a long time influence by the thermal stress between the chip and the substrate.
FIG. 1 is a cross-sectional view of a conventional flip-chip package structure. Referring to FIG. 1, the chip 110 is disposed on a substrate 120 by flip-chip bonding, and the chip 110 includes a plurality of bumps 112 for electrically connecting to a circuit structure 122 of the substrate 120. A solder mask 130 is disposed on the substrate 120 for covering a part of the circuit structure 122. Because the solder mask 130 needs to protect this part of the circuit structure 122 from being influenced during a soldering process, the solder mask 130 needs to maintain a certain thickness. However, if the interval H1 between the chip 110 and the solder mask 130 is too small, the underfill 140 cannot easily be filled in the interval between the chip 110 and the substrate 120, which may affect the reliability of the connecting between the bumps 112 and the circuit structure 122 of the substrate 120. What needed, therefore, is to increase the interval H1 between the chip 110 and the solder mask 130.